1. Field of the Invention
The present invention relates to fabrication of an oxide cathode or hanging-type oxide cathode used in an electron tube such as CRT, and more particularly to a jig for aligning/fixing the oxide cathode when screen-printing is carried out for applying a carbonate layer in the process of fabricating the oxide cathode, and a method of fabricating the oxide cathode using the jig.
2. Description of the Related Art
A previously known method of fabricating an oxide cathode is disclosed in JP-A-53-85418. This reference discloses a technique of subjecting the upper surface of a cathode body of a cathode for an electron tube to screen-printing to form a coarse Ni face of Ni paste and apply a carbonate layer after sintering. This technique, which can increase the surface area of the Ni coarse surface and adhesive force, realizes a cathode for an electron tube with stable quality.
Actually, when carbonate paste is applied on the metallic body of the oxide cathode by screen printing to form a carbonate layer, with a plurality of oxide cathodes being aligned, the carbonate paste can be simultaneously applied on the metallic body of each oxide cathode through a squeezing operation. The thickness of the carbonate paste applied by the screen printing influences the several characteristics of an electron tube, and hence a very important item to be managed in mass production of the oxide cathode. Therefore, it is desired that the carbonate layer of each of the oxide cathodes mass-produced has a required equal thickness. It is also desired that redundant carbonate paste does not flow onto the cylindrical sleeve side to which the metallic body is welded, and the sleeve or metallic body does not deform owing to load which necessarily occurs in contact of the oxide cathode with a screen during printing.
In order to solve these problems, it is required that the oxide cathodes to be subjected to printing are arranged so that the upper surface of the metallic body of each oxide cathode is in parallel to and uniformly apart from the screen. It is also required that the position of each metallic body is precisely aligned with the individual printing pattern of the screen. Therefore, it is necessary to use a jig which permits the upper position of the metallic body to be precisely located for the individual oxide cathode in its vertical, horizontal and twisting directions. In order to prevent the deformation of the sleeve or metallic body, a portion for supporting the screen so as to be flush with the metallic body must be installed within the jig.
An object of the present invention is to provide an oxide cathode aligning/fixing jig which permits a carbonate layer to be simultaneously applied on the upper surface of a metallic body of each of a large number of oxide cathodes by screen printing, thus improving the mass production efficiency and permits the oxide cathodes to be located precisely and easily to prevent and correct the deformation of the oxide cathodes.
Another object of the present invention is to provide a method of fabricating a plurality of oxide cathodes using the jig.
A first aspect is an oxide cathode aligning/fixing jig in which a plurality of oxide cathodes, each having a metallic body on an upper surface of which a screen-printing layer is to be applied, are aligned/fixed at regular intervals in a state where the upper surface of the metallic body is oriented upward.
A second aspect is an oxide cathode aligning/fixing jig according to the first aspect, wherein the upper surfaces of the metallic bodies are made flush with one another.
A third aspect is an oxide cathode aligning/fixing jig according to the second aspect, wherein each of said oxide cathodes is fixed at its bottom.
A fourth aspect is an oxide cathode aligning/fixing jig according to the third aspect, wherein each of said oxide cathode is fixed at its side.
A fifth aspect is an oxide cathode aligning/fixing jig according to the first aspect, wherein said plurality of oxide cathodes each includes a metallic body on an upper surface of which an electron radiative material layer is to be formed by screen-printing.
A sixth aspect is an oxide cathode aligning/fixing jig according to the first aspect, wherein said plurality of oxide cathodes each includes a metallic body on an upper surface of which a carbonate layer is to be formed by screen-printing.
A seventh aspect is an oxide cathode aligning/fixing jig according to the sixth aspect, wherein the upper surfaces of the metallic bodies are flush with one another.
An eighth aspect is an oxide cathode aligning/fixing jig according to the first aspect, wherein each said oxide cathodes is a hanging-type oxide cathode including a cylindrical sleeve at one end of which the metallic body is secured and an eyelet which surrounds a portion of the outer surface inclusive of the other end of said sleeve so as to protrude the metallic body and fixedly hangs said sleeve through a ribbon; and wherein said oxide cathode aligning/fixing jig includes
a plate-like upper fixing jig which have through-holes formed at regular intervals and fixedly supports the outer surface of said eyelet, the diameter of each said through-holes corresponding to the diameter of the eyelet; and PA1 a plate-like lower fixing jig which has sleeve bottom supporting members arranged to correspond to said through-holes in their position and fixedly supports the bottom of said sleeve, each said sleeve bottom supporting members being a cylinder having a diameter smaller than that of the eyelet and larger than that of said sleeve. PA1 a plate-like upper fixing jig which have through-holes formed at regular intervals and fixedly supports the outer surface of said eyelet, the diameter of each said holes corresponding to the diameter of the eyelet; and PA1 a lower fixing jig having cylinders each of which is structured to support the bottom of each said metallic bodies and internal surface of said sleeve, and has an end surface in contact with the bottom of each said metallic bodies having a smaller diameter than that of the other end surface. PA1 a plate-like upper fixing jig which have through-holes formed at regular intervals and fixedly supports the outer surface of said eyelet, the diameter of each said through-holes corresponding to the maximum diameter of said sleeve; and PA1 a plate-like lower fixing jig which has cylinders arranged to correspond to said through-holes in their position and fixedly supports the bottom of said metallic body and the internal surface of said sleeve. PA1 aligning and fixing said plurality of the metallic body for the oxide cathodes in said aligning/fixing jig so as to expose the upper surface of said metallic body; PA1 screen-printing carbonate paste on the upper surface of said metallic body by screen printing; and PA1 drying and baking said plurality of oxide cathodes.
A ninth aspect is an oxide cathode aligning/fixing jig according to the eighth aspect, wherein each said oxide cathodes is a hanging-type oxide cathode including a cylindrical sleeve at one end of which the metallic body is secured and an eyelet which surrounds a portion of the outer surface inclusive of the other end of said sleeve so as to protrude the metallic body and fixedly hangs said sleeve through a ribbon; and
Wherein said oxide cathode aligning/fixing jig includes
A tenth aspect is an oxide cathode aligning/fixing jig according to the first aspect, wherein each said oxide cathodes is composed of a metallic body and a sleeve with said metallic body secured to its one end, wherein said oxide cathode aligning/fixing jig includes
An eleventh aspect is an oxide cathode aligning/fixing jig according to the eighth aspect, wherein said sleeve bottom supporting members or cylinders of said lower fixing jig each has a sweeping hole at a position in contact with the bottom of said sleeve or metallic body.
A twelfth aspect is an oxide cathode aligning/fixing jig according to the eighth aspect, wherein said upper fixing jig is structured to protrude toward the center of the through-hole so that each said through-holes of said upper fixing jig has a smaller diameter at a portion in the vicinity of the metallic body when said oxide cathode is installed than the remaining portion, thereby constituting a sleeve side supporting member.
A thirteenth aspect is an oxide cathode aligning/fixing jig according to the eighth aspect, wherein the upper surface of said upper fixing jig is flush with that of said metallic body when each said oxide cathodes is arranged.
A fourteenth aspect is an oxide cathode aligning/fixing jig according to the twelfth aspect, wherein a depression is formed on the upper surface of said fixing jig corresponding to the end of said sleeve side supporting member, or a taper is formed downward toward the end of said sleeve side supporting member.
A fifteenth aspect is an oxide cathode aligning/fixing jig according to the fourteenth aspect, wherein said depression or taper has a size enough to prevent paste layer formed by screen-film printing from being applied to the side of said sleeve by the capillary action.
A sixteenth aspect is an oxide cathode aligning/fixing jig according to the twelfth aspect, wherein said sleeve side supporting member is formed to provide a minute gap between itself and the sleeve when said oxide cathode is installed.
A seventeenth aspect is an oxide cathode aligning/fixing jig according to the sixteenth aspect, wherein said minute gap has a size enough to prevent paste layer formed by screen-printing from being applied to the side of said sleeve by the capillary action.
An eighteenth aspect is a method of fabricating a plurality of oxide cathodes with a carbonate layer applied thereon using the oxide cathode aligning fixing jig according to the eighth aspect, which comprises the steps of:
By using the oxide cathode aligning/fixing jig according to the present invention, the metallic bodies of a plurality of oxide cathodes can be aligned at equal heights, and the vertical and horizontal positions of the oxide cathodes can be secured precisely. For this reason, when the carbonate paste is applied by the screen printing, a carbonate layer having a uniform thickness can be obtained with a suppressed variation in printing pattern(thick film). Since the carbonate layer can be applied for a large number of oxide cathodes at a time, the mass-production efficiency can be increased.
By using the oxide cathode aligning/fixing jig according to the present invention, in addition to the above advantage, during the process of fabricating the hanging-type oxide cathode, the displacement between sleeve and eyelet due to the deformation of the ribbon can be corrected.
When the oxide cathode aligning/fixing jig according to the present invention is used, the upper surface of the upper member of this jig is adjusted to be flush with the upper surface of the metallic body on which the carbonate paste is applied when the oxide cathode is installed. In the case where the printing is carried out with a squeeze being pressed downward, the force applied to the metallic body can be dispersed, thus deforming the oxide cathode.
By using the oxide cathode aligning/fixing jig according to the present invention, in which a depression, taper or spot-facing is formed at a position corresponding to a sleeve supporting of the edge of the cut-hole on the surface of the upper fixing jig, it is possible to suppress the flow of the carbonate paste to the sleeve side by the capillary action when the carbonate paste is screen-printed.
By fabricating the oxide cathodes using the oxide cathode aligning/fixing jig described above, the carbonate layer having a uniform thickness can be formed for a large number of oxide cathodes at a time, and the positioning accuracy in printing can be also improved.